Quercus robur

Grandinin/roburin E, castalagin/vescalagin, gallic acid, monogalloyl glucose (glucogallin) and valoneic acid dilactone, monogalloyl glucose, digalloyl glucose, trigalloyl glucose, rhamnose, quercitrin and ellagic acid are phenolic compounds found in Q. robur.[11] The heartwood contains triterpene saponins.[12]

• Quercus robur 'Fastigiata' ("cypress oak"), probably the most common cultivated form , it grows to a large imposing tree with a narrow columnar habit. The fastigiate oak was originally propagated from an upright tree that was found in central Europe.
• Quercus robur 'Concordia' ("golden oak"), a small very slow-growing tree, eventually reaching 10 m (33 ft), with bright golden-yellow leaves throughout spring and summer. It was originally raised in Van Geert's nursery at Ghent in 1843.
• Quercus robur 'Pendula' ("weeping oak"), a small to medium-sized tree with pendulous branches, reaching up to 15 m.
• Quercus robur 'Purpurea' is another cultivar growing to 10 m, but with purple-coloured leaves.
• Quercus robur 'Filicifolia' ("cut-leaved oak") is a cultivar where the leaf is pinnately divided into fine forward pointing segments.

Along with the naturally occurring Q. × rosacea, several hybrids with other white oak species have also been produced in cultivation, including Turner's Oak Q. × turneri, Heritage Oak Q. × macdanielli, and Two Worlds Oak Q. × bimundorum, the latter two developed by nurseries in the United States.

• Q. × bimundorum (Q. alba × Q. robur) (two worlds oak)
• Q. × macdanielli (Q. macrocarpa × Q. robur) (heritage oak)
• Q. × rosacea Bechst. (Q. petraea x Q. robur), a hybrid of the sessile oak and English oak. It is usually of intermediate character between its parents, however it does occasionally exhibit more pronounced characteristics of one or the other parent.
• Q. × turneri Willd. (Q. ilex × Q. robur) (Turner's oak), a semi-evergreen tree of small to medium size with a rounded crown; it was originally raised at the Holloway Down Nursery of Spencer Turner, Leyton, Essex, UK, noted by the zoologist Jean-Baptiste Lamarck at Trianon, Versailles in 1783, as the chêne de turnère.[19] (Turner had died in January 1776, and the nursery grounds, on extended lease, returned to the landowner.)[20] An early specimen was planted at the Royal Botanic Gardens, Kew in 1798; it was uprooted in the Great Storm of 1987 but resettled in the ground and then increased its healthy growth.[21]
• Q. × warei (Q. robur fastigiata x Q. bicolor), a hybrid between upright English oak and the swamp white oak. The selections within this hybrid include 'Long' (Regal Prince)[22] and 'Nadler' (Kindred Spirit).[23]

• Acute oak decline
• Powdery mildew caused by Erysiphe alphitoides[24]
• Sudden oak death

In the Basque Country (Spain and France) the oak symbolises the traditional Basque liberties. This is based on the 'tree of Gernika', an ancient oak tree located in Gernika, below which since at least the 13th century the Lords of Biscay first, and afterwards their successors the Kings of Castile and the Kings of Spain solemnly swore to uphold the charter of Biscay, which secured widespread rights to the inhabitants of Biscay. Since the 14th century, the Juntas Generales (the parliament of Biscay) gathers in a building next to the oak tree, and symbolically passes its laws under the tree as well. Nowadays, the Lehendakari (Basque prime minister) swears his oath of office under the tree.

The national coat of arms of Bulgaria includes two crossed oak branches with fruits – as shield (escutcheon) compartment.

Oak leaves with acorns are depicted on the reverse of the Croatian 5 lipa coin, minted since 1993.[26] The pedunculate oak of the Croatian region of Slavonia (considered a separate subspecies – Slavonian oak) is a regional symbol of Slavonia and a national symbol of Croatia.[27]

In traditional Finnish culture, the oak is considered a holy tree.[28] In Finnic mythology, the World tree, which supported the sky, was a great oak, which grew to block the movement of the sky, sunlight and moonlight, and had to be felled, releasing its magic, creating the Milky Way, which guides dead souls to the afterworld.[28][29] The oak was also considered to have many magical properties, and it was used in traditional Finnish folk medicine as well.[28]

In 1746, all oak trees were legally classified as royal property (at the time Finland was a part of Sweden), and oaks had enjoyed legal protection already from the 17th century.[30]

The oak is also the regional tree of the Southwest Finland region,[31] where it is a common yard tree.[32]

The oak tree has had a symbolic value since Ancient times. Some oaks were considered sacred trees by the Gauls. The druids would cut down the mistletoe growing on them. Even after Christianization, oak trees were considered to protect as lightning would strike them rather than on nearby inhabitation. Such struck trees would often be turned into places of worship, like the Chêne chapelle. King Saint Louis has been represented rendering justice under an oak tree. During the French Revolution, oaks were often planted as trees of freedom (fr). One of such trees, an oak planted during the 1848 Revolution, survived the destruction of Oradour-sur-Glane by the Nazis. The branch of oak is part of the National emblem of France. After the announcement of General Charles de Gaulle's death, caricaturist Jacques Faizant represented him as a fallen oak.

In Germany, the oak tree (regional known as "German Oak") is used as a typical object and symbol in romanticism. It can be found in several paintings of Caspar David Friedrich and in "Of the life of a Good-For-Nothing" written by Joseph Freiherr von Eichendorff as a symbol of the state protecting every citizen. In those works the oak is shown in different situations, with leaves and flowers or dead without any of its previous beauty. Those conditions are mostly symbols for the conditions Germany is in or going through. Furthermore, the oak's stem is a symbol for Germany's strength and stability. Oak branches were displayed on the reverse of coins of the old Deutsche Mark currency (1 through 10 Pfennigs; the 50 Pfennigs coin showed a woman planting an oak seedling), and are now also displayed on the reverse of German-issue Euro currency coins (1 through 5 cents).

In Ireland, at Birr Castle, a specimen over 400 years old has a girth of 6.5 m (21 ft). It is known as the Carroll Oak, referring to the local Chieftains, Ely O'Carroll who ruled prior to Norman occupation.[33]

In Latvia oak is the national symbol. Many Latvian folk songs are about oak tree. Base of the coat of arms is decorated with the branches of an oak tree.

The Romanian Rugby Union side is known as The Oaks.

Oak pictured in the coat of arms of Ekenäs

In the Scandinavian countries, oaks were considered the "thunderstorm trees", which representing Thor, the god of thunder.[34]

In England, the English oak has assumed the status of a national emblem. This has its origins in the oak tree at Boscobel House, where the future King Charles II hid from his Parliamentarian pursuers in 1650 during the English Civil War; the tree has since been known as the Royal Oak. This event was celebrated nationally on 29 May as Oak Apple Day, which is continued to this day in some communities.[35] 'The Royal Oak' is the third most popular pub name in Britain (with 541 counted in 2007)[36] and has been the name of eight major Royal Navy warships. The naval associations are strengthened by the fact that oak was the main construction material for sailing warships. The Royal Navy was often described as 'The Wooden Walls of Old England'[37] (a paraphrase of the Delphic Oracle) and the Navy’s official quick march is "Heart of Oak". In folklore, the Major Oak is where Robin Hood is purportedly to have taken shelter.[38] Furthermore, the oak is the most common woodland tree in England.[39] An oak tree has been depicted on the reverse of the pound coin (the 1987 and 1992 issues) and a sprig of oak leaves and acorns is the emblem of the National Trust.